The present invention relates to a method for the determination of the actual speed of a movable displacement element. An acceleration sensor is used to record an acceleration of the displacement element and a model speed of the displacement element is determined by integrating the acceleration. A position sensor is used to record a measured position of the displacement element, and a measured speed of the displacement element is determined by differentiating the measured position. The actual speed is determined on the basis of the model speed.
A determination method is disclosed, by way of example, in xe2x80x9cDrehbeschleunigungssensor ermxc3x6glicht hochgenaue Drehzahlregelungxe2x80x9d (xe2x80x9cRotary Acceleration Sensor Allows High Precision Rotation Speed (control)xe2x80x9d) by Lothar Wilhemly and Reinhard Domke, offprint from xe2x80x9cAntriebstechnikxe2x80x9d April 1999. A similar disclosure can be found in the paper xe2x80x9cRelativbeschleunigungssensorxe2x80x94Potential und Einsatzmxc3x6glichkeiten in der Servo-Antriebstechnikxe2x80x9d (Relative Acceleration Sensorxe2x80x94Potential and Opportunities For Use In Servo Drive Technology) by W. Hiller, ISW, Stuttgart, given at the ISW position control seminar 1998.
In such determination methods, the recorded acceleration must remain free of offset so that the model speed does not drift. In the latter of the above-mentioned publications, this is achieved by supplying the recorded acceleration and the measured position to an xe2x80x9cobserverxe2x80x9d with the observer determining therefrom an offset for the recorded acceleration, which is then eliminated. The reference also mentions the design of a secondary acceleration control loop as an alternative.
The object of the present invention is to provide a determination method of the type mentioned in the introduction wherein in which any acceleration offset can be compensated for as simply as possible and yet with a high degree of precision.
This object is achieved as a result of the model speed and the measured speed being subtracted from one another, and the difference being supplied to a controller having an integral component, preferably to a PI controller, the output signal of which is added to the acceleration.
If the model speed is supplied with a time delay to the controller having an integral component, it is possible to compensate for the offset using a relatively high control dynamic range.
If the controller, having an integral component, has controller parameters which can be set in situ, the controller parameters can be matched in situ to the circumstances specifically prevailing there.
If a model position is determined by integrating the actual speed, and the model position is used to determine an actual position, the acceleration can also be used to calculate the actual position.
If the actual position and the measured position are subtracted from one another and the difference is supplied to a P controller whose output signal is added to the actual speed, the actual position can also be determined without an offset.
If the actual position has a time delay with respect to the model position, the control works more precisely.
If the P controller has controller parameters which can be set in situ, the controller parameters can be matched in situ to the circumstances specifically prevailing there.